From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17FD6C433F5 for ; Wed, 17 Nov 2021 11:24:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EFB9861B97 for ; Wed, 17 Nov 2021 11:24:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236769AbhKQL1h (ORCPT ); Wed, 17 Nov 2021 06:27:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233972AbhKQL1g (ORCPT ); Wed, 17 Nov 2021 06:27:36 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 04CBAC061570 for ; Wed, 17 Nov 2021 03:24:38 -0800 (PST) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mnJ3F-0006ji-PW; Wed, 17 Nov 2021 12:24:29 +0100 Received: from [2a0a:edc0:0:900:1d::77] (helo=ptz.office.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mnJ3B-000M5S-Gz; Wed, 17 Nov 2021 12:24:24 +0100 Received: from ukl by ptz.office.stw.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1mnJ3A-0003az-75; Wed, 17 Nov 2021 12:24:24 +0100 Date: Wed, 17 Nov 2021 12:24:00 +0100 From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= To: cgel.zte@gmail.com Cc: thierry.reding@gmail.com, lee.jones@linaro.org, nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, ludovic.desroches@microchip.com, linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Changcheng Deng , Zeal Robot Subject: Re: [PATCH] pwm: Use div64_ul instead of do_div Message-ID: <20211117112400.bkscb2pyavonpfsn@pengutronix.de> References: <20211117020426.159242-1-deng.changcheng@zte.com.cn> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mjecz3xyrkcwg42p" Content-Disposition: inline In-Reply-To: <20211117020426.159242-1-deng.changcheng@zte.com.cn> X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --mjecz3xyrkcwg42p Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello, On Wed, Nov 17, 2021 at 02:04:26AM +0000, cgel.zte@gmail.com wrote: > From: Changcheng Deng >=20 > do_div() does a 64-by-32 division. If the divisor is unsigned long, using > div64_ul can avoid truncation to 32-bit. After some research I understood your commit log. I'd write: do_div() does a 64-by-32 division. Here the divsor is an unsigned long which on some platforms is 64 bit wide. So use div64_ul instead of do_div to avoid a possible truncation. The priority of this patch seems to be low, as the device seems to exist only on (32bit) arm. > diff --git a/drivers/pwm/pwm-atmel-hlcdc.c b/drivers/pwm/pwm-atmel-hlcdc.c > index a43b2babc809..1ae3d73b9832 100644 > --- a/drivers/pwm/pwm-atmel-hlcdc.c > +++ b/drivers/pwm/pwm-atmel-hlcdc.c > @@ -60,7 +60,7 @@ static int atmel_hlcdc_pwm_apply(struct pwm_chip *c, st= ruct pwm_device *pwm, > return -EINVAL; > =20 > clk_period_ns =3D (u64)NSEC_PER_SEC * 256; > - do_div(clk_period_ns, clk_freq); > + div64_ul(clk_period_ns, clk_freq); This must be clk_period_ns =3D div64_ul(clk_period_ns, clk_freq); as div64_ul has a different calling convention than do_div. Same problem in the next hunk. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | https://www.pengutronix.de/ | --mjecz3xyrkcwg42p Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAmGU5k0ACgkQwfwUeK3K 7An4+Af+OP2VhxA5quV4sEd1vi1tJowfr76mjpf4Z2zzOGA56nPX+wnz/g0Jaa+B Kag+Hnr/ycZw77SUzbWh4DotdoJA0uja+IystuQYVs31R4s7vTbI3jk/0zl8baws S4A3t5Fk6oUl04rRvVvwUMWhrxt8sqk803YO0APqcy0X6SOcsMHnXmOVZdiDJ+cl I6HJu5JAQ4tJ5B6MBgXYA3fYWhbagxtxQEpa4z5plYYtoJ3RvuBSWETskmFxrCVT LXYD+P6Ft9wQOd/lxHrcss/eVVjZKWJ9amxZnInW7g0HLVMtRXZN0z+uuP6Go+2V tZXmGQxqWtQavVAS8b1aL1GG64dG1g== =E16E -----END PGP SIGNATURE----- --mjecz3xyrkcwg42p--